Ice bank control



Nov. 29, 1955 J, J, ROTHWELL 2,724,950

ICE BANK CONTROL Filed May 3, 1952 0 In .me/z for. rfa/Erz z/ @f/:#4922,

avllillllllllllllil United States Patent O ICE BANK CONTROL Applicatihn May 3, 1952, Serial N o. 285,939

'A 4 claims. (C1. 62-7) This invention relates in general to a controller for the operation of a refrigerant compressor that supplies refrigerant to an evaporator in a milk cooier or similar type of apparatus wherein it is desired to maintain an` ice bank of predetermined size.

One object of: the invention is to provide for accurate control of the thickness of the ice bank within very close limits, yet without the necessity of having a control that operates ata close differential.

Another object is to provide an ice bank control which is reliable as to its operation regardless of the character of the water that forms the ice bank itself.

More specifically it is an object to provide an ice bank control which uses the Water that subsequently forms the ice bank as a means to plug up normally open portions of a pressure generating housing so that when the ice bank builds up to a desired point it will create a pressure in the housing that is of sufficient magnitude that it can be utilized to perform a control function.

A further object is to provide an ice bank control in the form of a pressure generating housing spaced from an evaporator and having upper and lower ports which are imbedded in the ice bank that forms on the evaporator (which is submerged in water) so that ice forms in the ports and plugs them against escape of pressure, after which further formation of ice builds up a pressure in the housing which pressure is transmitted to a pressure operated control switch or the like adapted for controlling the circuit of a refrigerant compressor motor.

Still a further object is to increase the effectiveness of the ice plugs by means of a pair of tubes which enter the ports of the housing and are open at their extremities, the tubes being of substantial length and preferably past the evaporator coils.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of my ice bank control, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawings, wherein:

Figure 1 is a cross section through a milk cooler show ing my ice bank control mounted therein and includes a diagram of the connection thereof to the refrigerant compressor motor as well as a diagram of the refrigerant system for the evaporator of the milk cooler;

Figure 2 is an enlarged portion of Figure 1 showing the main portion of my control in section and illustrating its operation; and

Figure 3 is a sectional View of a modified form of the invention.

On the accompanying drawing I have used the reference numeral 10 to indicate a tank such as one of the insulated wall type used to contain an ice bank for milk cooling purposes. The ice bank is shown at 12 and a pair of milk cans 14 are illustrated to show the environment. The cover of the tank is shown at 16.

Tanks of this character are usually provided with an `evaporator coil 18 extending around the inside of the 'ice tank and spaced somewhat from the wall. These coolers are initially filled with water indicated at 20, a portion of which is fro-zen to form the ice bank 12 upon initial prolonged operation of the refrigeration system.

'Ihe system is shown diagrammatically in Figure 1, the refrigerant compressor being illustrated at 22, the refrigerant compressor motor at 24, the condenser at 26 and the expansion valve at 23 together with suitable connections to the evaporator coil 18.

My ice bank control consists in general of a pressure generating housing A, a pressure receiving housing B, a capillary pressure transmission tube 3i) between the two, and a control switch C for the current supply to the motor 24. The switch C may be of conventional construction and is illustrated diagrammatically with a stationary contact 32 and a movable contact 34 for controlling the circuit, the movable contact being mounted on an arm 36 under control of a pin 38 extending from a diaphragm 40 of the pressure receiving housing B. Opposing the pressure is a spring 42, which may be adjusted at 44 to set the operating point of the control.

While the parts B and C are of more or less conventional construction, the pressure generating housing A is of novel construction and constitutes the main element of my ice bank control. It will now be specifically described in detail.

The pressure generating housing A comprises a pair of housing parts 46 and 48 which may be soldered together with a diaphragm 59 between them. Thus there are two chambers 52 and S4 in the housing separated by the diaphragm. A pressure transmission fluid 56 is contained in the chamber S4 as well as in the tube 30 and the pressure receiving housing B above the diaphragm 40 whereby movement toward the right of the diaphragm 50 in Figure 2 will move the diaphragm 4t) downwardly in Figure 1 for opening the switch 3h34 as shown. The fluid 56 may be introduced through a short tube 72 to completely fill the pressure transmission system (chamber 54, capillary tube 30 and pressure chamber B) after which the tube 72 may be pinched off and solder-sealed at 74.

An upper tube 58 and a lower tube 60 are connected with the housing member 48 and open into the chamber S2. The extremities of these tubes indicated at 62 and r 64 respectively are open to atmosphere within the tank 10, the opening 62 being preferably restricted. The tubes 58 and 60 preferably extend from the pressure generating housing A back toward the evaporator coil 18 and have respectively an upwardly extending part 58a and a horizontally extending part 60a which are located between the evaporator coil 18 and the wall of the tank 1t) as illustrated. The parts 58a and 60a may be approximately equal in length. The opening 62 is restricted to minimize the possibility of dirt or other foreign matter entering the tube 58 but does not interferev with the free exit and entrance of air during cooler filling and draining operations which will be described later. The open end 64, however, is not restricted so as to permit free entry and exit of water during the filling and draining operations.

Alternatively the housing A may be used without the tubes 5S and 60 as in Figure 3. The housing is then open at its top (at 62:1) and at its bottom (at 64a) to the interior of the tank. A unit of this type operates satisfactorily but its performance is improved somewhat by the addition of the tube as in Figure 2.

Support for the pressure generating housing A maybe conveniently provided in the form of a bracket 66 connected to the housing part 48 and clamped by a clamp 66 and a clamp screw 7i) to one run of the evaporator coil 18.

Practical operation In^'the'operation" of my ice' bank'control, assumingfirstr that the tank 10 is empty, the user lls it with water to the approximate level shown in Figure l.. As the water rises in'the tank itenters the open end`6'4 oflthe. tube. 60,' llsthis tube', then the chamber 52and'f1nally the tube 58', the air in 60, 52and'58. being displacedby the rising water andp'assingout of the open end 62of the tube 5S. The same entry of water through the port 64a and'displacement of air through the port 62h occurs with the type oflpressure generating housing shown in Figure 3. Thus when the tank 10 is lledto theproper level, the chamber 52 of the pressure generating housingA to the left of the diaphragm 50 is likewise filled with the same water.

When currentk is initially supplied to the refrigerantI eration systemA operates, ice will start forming on the coil i IS'randlwill be built up finally to approximately the thickness shownin Figures 1 and'2. The first build-up of ice around each run of the coil 18 such as indicated by the dotted circles 26u in Figure 2 will start forming ice in the-tubes 58 and'otl and this ice will have a tendency to plug the tubes so that pressure can be subsequently built up in the chamber 52 of the pressure generating housing A and be utilized to stop the operation of the refrigeration system I' have found, however, that this action does not occur until the ice bank builds up to such a point' that it reaches the housing A and starts forming around it. Experimentation seems to indicate that' the initial plugs of ice in the tubes S and 6G are porous and therefore permit some leakage of pressure, and it is not until a substantial ice bank has been formed and the ice rendered non-porous that enough pressure can be developed to displace the diaphragm 50'toward the right in Figure 2 sufficiently to operate the control switch C.

Such operating pressure results. from the expansion which occurs as the water changes to ice, the volume of water to ice being approximately 1.0 to 1.0855 (about an 81/2% increase). I assume that the ice builds up about as indicated at 12b in Figure 2 within the pressure generating housing A before the required pressure is developed as the switch 32-34 opens when the ice bank forms around the housing Ato approximately the extent shownl in both figures` of the drawing` In practice, I have found that pressures between 2() lbs. and. 60 lbs. can be developed in the housing A and that a small: differential of pressures within this range will operate the control switch C to operate the refrigeration system about one hour in a twelve-hour period and maintain the ice bank 12 within lf2 differential in ice thickness.

I have also found that the plugging up of the tubes 58 and 60 is somewhat facilitated by extending them into close proximity to the coil I8 and by having. the portions. 58a and 80a between the evaporator and the tank wall, although various arrangements of the tubes other than those illustrated as well as the arrangement of Figure 3' will operate satisfactorily. In any event, it seems desirable when tubes are. used for the water to rise in them properly without trapping air, and when the tank l is drained such as during winter weather, it is'` desirable thatI the water likewise drain. out of the housing. A and the tubes 58 and 60 if used. This is also important from the standpoint of subsequent filling of the tank 10 which might be with water having a different chemical or mineral composition.

I have found it necessary to have the same water in the ice bank control as the water used for formingthe ice bank. Otherwise the freezing point within the ice bank control might be different than the freezing point of the ice bank itself and the control would not operate properly. In this connection I have experimented with ice bank controls within which a chargeof water was sealed and it was extremely diticult to get proper control because the charge, of water, ,in ,order to4 .prevent corrosion .of the` pressure generating housing, must be distilled or inert with respect to the metal of the housing, and the metal of the housing itself may contaminate the sealed charge of water so that the freezing point shifts and in most instances is different than the ordinary run of water that would be used in the tank 10^surrounding the ice bank control.

Therefore arrangements such as I propose always utilize the same Water as that inthetank 10. Thislis an imporf tant consideration and onewhich isadmirably-taken'care of by permitting filling and draining of.l the iceA bank control each time the tank 10 is lled and drained.

Some changes may be madeiin. the construction and arrangement of the parts of my ice bank control without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical'equivalents which may be reasonably included within-theirscope.

I claim as my invention:

l. A control'device fora cooling container of the typeincluding a tank, an evaporator inside'the tank in spaced relation to the walls thereof, a refrigerant system for the evaporator, water in said tank, a portion of said-water adjacent the tank walls being frozen to form an ice bank by operation of the refrigerant system and-cooling ofthe evaporator, and a pressure responsive actuating means to control the starting and shutting oif of the refrigerantI system, said control device comprising-a pressure generating housing mounted inside said tank in spaced relation tothe evaporator, a pressure responsive means in said said tank to provide entry of the water which forms said ice bank.

2. A control device for aV cooling container of the type including a tank, an evaporator inside the tank in spaced relation to the walls thereof, a refrigerant system for the evaporator, water in saidy tank, a portion of said water adjacent the tank walls being frozen to form an ice bank by operation of the refrigerant system and cooling of the evaporator, and a pressure responsive actuating means to controly the starting and shutting off of the refrigerant sys` tem, said control device comprising a pressure generating housing mounted inside said tank in spaced relation to the evaporator, a pressure responsive means in said housing dividing said housing into a first and asecond chamber, means for transmitting pressure from said second chamber to said pressure responsive actuating means, said pressure transmitting means and said second chamber forming a closed system with said pressure responsive actuating means, and means communicating with said first chamber and said tank to provide entry of the water which forms said ice bank.

3. A control device for a cooling container of the type including a tank, an evaporator inside the tank in spaced relation to the walls thereof, a refrigerant system for the evaporator, water in said tank, a portion of said water adjacent the tank walls being frozen to form an ice bank by operation of the refrigerant system and cooling of the evaporator, and a pressure responsive actuating means to.

control the starting and shutting off of the refrigerantl system, said control device comprising a pressure generating housing mounted inside said tank in spaced relation to the evaporator, a pressure responsive means in said housing dividing said housing into rst and second chambers, means for transmitting pressure from said second chamber to said pressure responsive actuating means, and means communicating with said rst chamber and said tank to provide entry of the water which forms saidv ice bank, said last means comprising an upper tube and a lower tube open at their extremities to the interior of the tank and extending from said rst chamber toward the evaporator so as to be imbedded in the ice bank formed thereby.

4. A control device for a cooling container of the type including a tank, an evaporator inside the tank in spaced relation to the walls thereof, a refrigerant system for the evaporator, water in said tank, a portion of said water ad jacent the tank Walls being frozen to form an ice bank by operation of the refrigerant system and cooling of the evaporator, and a pressure responsive actuating means to control the starting and shutting off of the refrigerant system, said control device comprising a pressure generating housing mounted inside said tank in spaced relation to the evaporator, a pressure responsive means in said housing dividing said housing into a first and a second chamber,

6 means for transmitting pressure from said second chamber to said pressure responsive actuating means, and openings at the top and bottom of said housing to permit free entry into said rst chamber of the water which forms said ice bank.

References Cited in the file of this patent UNITED STATES PATENTS 1,745,859 McElroy Feb. 4, 1930 2,187,258 Wood Jan. 16, 1940 2,359,168 Somes Sept. 26, 1944 2,512,066 Linfor June 20, 1950 2,561,437 Cobb July 24, 1951 

